The capacity of communities to bolster and sustain the well being of individual residents is particularly salient for older adults; their daily activities are likely dependent on the infrastructure and social resources of their communities, particularly if health is already compromised. Although it has long been believed that the neighborhood one lives in affects one's health, it has been difficult to delineate why, and under what circumstances, neighborhood context contributes to health. We bring an important new sociological concept, collective efficacy, to bear on the study of neighborhood and the health of older persons. Using data from the Project on Human Development in Chicago Neighborhoods-Community Survey, the Metropolitan Community Information Center-Metro Survey, Medicare Claims, and out-patient, hospitalization, and geocoded health services data, we ask: 1) Are structural features of urban neighborhoods--concentrated poverty, concentrated affluence, residential stability, ethnic heterogeneity, and age structurel associated with the health status of older residents?; 2) Are neighborhood social processes--collective efficacy, social networks, social norms, and physical/social disorder associated with the health of older residents?; 3) is the health services infrastructure of the neighborhood associated with the health of older residents?; and 4) Does the health of older residents affect the ability of the community to sustain social networks and develop collective efficacy? This project goes beyond current research in four ways. First, it extends existing research on neighborhood context and the health of older adults by exploring theoretically informed mechanisms with multi-level statistical tools. Second, it incorporates an understudied area in the neighborhood effects literature--the role of health services and access to care. Simultaneously examining the effects of neighborhood context and health services could enhance our understanding of individual-level racial/ethnic and socioeconomic disparities in health. Third, it acknowledges that the relationship between neighborhood and health is both reciprocal and dynamic. Fourth, it provides a unique opportunity to examine interactions across a number of levels (e.g., individual-neighborhood, neighborhood-health services infrastructure). This project combines perspectives from sociology and health services research; it bridges these disciplines to formulate research that addresses a set of questions vital to both fields and to aging-related policy.